Your line 2 there does nothing. The only way you could really change anything here is by using System.arrayCopy(), which performs essentially the same operation as the loop you've written. Looks like that website doesn't let you do that, though.

Well arrayCopy() doesn't do output, so there's no technical reason to disallow that specific method. Interesting that they allowed Arrays, without a package name; they must be importing stuff from java.util behind the scenes.